The present invention relates to elevators and, more particularly, to a novel sheave design for improved performance and durability.
Conventional elevator systems have long utilized standard elevator ropes to suspend and move elevator cars. In order to optimize performance in such areas as traction, durability, ride quality and safety, numerous design parameters have limited various components such as motors, sheaves and rope grade to certain sizes, weights and dimensions.
New generation elevator systems are being developed that eliminate the need for various conventional components, through the implementation of superior performing traction and drive systems and other advancements. These types of systems offer many advantages over traditional elevator systems, including structural versatility and economy, convenient access for servicing and repair, and lighter building loads.
One particular advancement is the implementation of high-traction, high durability elevator ropes that are smooth running, light in weight and corrosive-resistant. One such type of rope is made of a plurality of tension-carrying cord members contained in a unitary insulation jacket made of, for example, a urethane material. For optimum performance with such ropes, it is desirable to adapt various components such as sheaves to interface closely.
Conventional elevator sheaves are cast iron and designed to accommodate traditional round, steel wire ropes. With the increasing feasibility of new generation elevator ropes, such as elastomer-coated, flat ropes, new problems related to tracking, traction and durability must be addressed. It is an object of the present invention to provide a sheave design having particular dimensional, geometric, and surface characteristics selected for optimum performance and durability for use with such new generation elevator ropes.
This object and others are achieved by the present invention sheave design. The present invention sheave design provides a convex contact surface defined by a crown height and crown radius dimension related to rope or belt width for tracking. Another aspect of the invention relates to a sheave design in which sheave groove width is related to belt width for tracking. Another aspect of the invention relates to providing a particular circumferential roughness to the contact surface for traction. The circumferential surface roughness is preferably about 1.0 to about 3.0 microns. Yet another aspect of the invention relates to providing a hard, corrossion-resistant coating on the sheave contact surface for improved durability. The coating preferably has a thickness of about 1-2 microns. The coating preferably has a hardness of greater than about 40 HRC.